Cassette tape recorders which record and reproduce analog signals on an analog compact cassette [hereinafter referred to as C-cassette) shown in FIGS. 11(a), (b) and (c)] are widely used. However, in view of such factors as the internal structure, tape material and the analog recording and reproduction system of the C-cassette, further improvement in the quality of reproduced sound is not expected.
With such a background, in recent years, there have been proposals to develop a digital compact cassette (hereinafter referred to as D-cassette) which has dimensions almost equal to those of the C-cassette. The proposals concern a device that can not only record and reproduce digital signals on the D-cassette, but can also play conventional C-cassettes. In order to achieve recording and reproduction of digital signals, the material for the magnetic tape of D-cassette is restricted and various measures are taken to provide a smooth running of the magnetic tape. The D-cassette with a size substantially equal to that of the C-cassette enables digital recording and reproduction, thereby improving sound quality.
With particular reference to FIGS. 11(a)(b)(c) through 13(a)(b)(c), the following discussion contrasts the conventional C-cassette and the D-cassette.
The C-cassette 1 shown in FIGS. 11(a)(b)(c) has a cassette container la holding a magnetic tape 1b. Formed in the front edge of the C-cassette 1 is an opening 1d for allowing a head to record and reproduce information on the magnetic tape 1b. Formed on each side of the opening 1d is an opening 1e into which a pinch roller is to be inserted. As shown in the plan view, trapezoidal portions 1f of the front and back sides extending from one opening 1e to the other opening 1e are outwardly raised, respectively. Two capstan holes 1g and two positioning holes 1h are symmetrically formed to extend through both front and back sides of the C-cassette 1.
Formed symmetrically near the center of the cassette container la are two reel holes 1i extending through the front and back sides thereof. Two reels, not shown, around which the magnetic tape 1b is wound, are disposed in the cassette container 1a. The cassette container 1a has side projections 1j formed on the side edges in the vicinity of the front edge. The side projections 1j are provided so that the user easily holds the C-cassette when loading or unloading the C-cassette into/from the cassette tape recorder. Nowadays, however, this original effect of the side projections 1j is less significant.
As for a D-cassette 2 shown in FIGS. 12(a)(b)(c) and 13(a)(b)(c), like the C-cassette 1, a cassette container 2a holds magnetic tape 2b. Unlike the C-cassette 1, the D-cassette 2 has no raised portions 1f and projections 1j, but has side recessions 2c at positions corresponding to the side projections 1j and has side recessions 2d formed in each side edge in the vicinity of the rear edge. The back side of the cassette container 2a has hollow sections 2e formed at positions corresponding to the reel holes 1i of the cassettes container 1a. The hollow sections 2e do not extend to the front side of the cassettes container 2a, and therefore the front side has no holes. The front edge of the cassette container 2a has an opening 2f for allowing a head to engage with the magnetic tape 2b to perform a recording or reproducing operation, and openings 2g, formed on each side of the opening 2f, for pinch rollers. A label 2h is pasted on the front side of the cassette container 2a. Formed above the right opening 2g is a guide recession 2k for guiding the movement of a slider 3 to be described later. Looking at the D-cassette from the front, the guide recession 2k is substantially triangular in shape and has a slanting guide surface 2i and a contact surface 2j. Formed in the back side of the cassette container 2a are two capstan holes 2m and two positioning holes 2n which are arranged symmetrically in the vicinity of the front edge.
The biggest difference between the cassettes 1 and 2 is that the D-cassette 2 has the slider 3. Namely, whilst the opening 1d and the openings 1e of the C-cassette 1 are always uncovered, the opening 2f and the openings 2g of the D-cassette 2 are covered with the slider 3 when the D-cassette 2 is not used.
The slider 3 is made of a thin metal plate which has two right-angled corners in profile, and covers partially the front edge, and front and back sides of the cassette container 2a. The slider 3 is freely moved in the A-B direction and always pushed toward the B direction by a spring, not shown.
The front edge of the slider 3 has an opening 3a and an opening 3b corresponding to the opening 2f and the left opening 2g of the D-cassette 2, respectively. Looking at the D-cassette 2 from the back, the back side of the slider 3 has a reel hole 3c corresponding to the left hollow section 2e, positioning holes 3d corresponding to the positioning holes 2n, and a capstan hole 3e corresponding to the left capstan hole 2m.
When the slider 3 is moved in the B direction, as shown in FIG. 12(c), the opening 2f and the openings 2g are covered with the slider 3 and the magnetic tape 2b in the cassette container 2a is protected. At this time, the guide recession 2k except the right slanting guide surface 2i is covered with the slider 3.
As illustrated in FIG. 13(c), when the slider 3 is moved in the A direction, the opening 3a and the opening 3b of the slider 3 are aligned with the opening 2f and left opening 2g, respectively, and uncover the openings 2f and 2g. The movement of the slider 3 in the A direction is driven by a slider moving mechanism. Specifically, when the slider moving mechanism is inserted into the guide recession 2k, it comes into contact with the slider 3 and moves in the A direction, thereby moving the slider 3 in the A direction.
The side recessions 2d of the cassette container 2a are called changer grips in general and allow the D-cassette 2 to be compatible with a cassette tape recorder having a changer function. The cassette tape recorder with the changer function has a cassette storage section capable of storing a plurality of D-cassettes 2, and records and reproduces information on/from a cassette selected from the D-cassettes 2 in the cassette storage section. The side recessions 2d are used as holes for holding the selected D-cassette 2 when moving it from the cassette storage section to the record/reproduction position. Meanwhile, the side recessions 2c are generally called storage grip and used as holes holding the D-cassette 2 when carrying it to the record/reproduction position for recording and reproduction.
The following description explains the dimensions of the C-cassette 1 and of the D-cassette 2. The C-cassette 1 has a length L.sub.c of 100.4 mm, a width M.sub.c of 63.8 mm, a thickness N.sub.c.spsb.1 (without including raised portions 1f) of 8.6 mm (tolerance: +0.3 mm, -0.1 mm), and a thickness N.sub.C.spsb. (including raised portions 1f) of 12.0 mm (tolerance: +0.3 mm, -0.1 mm). The length L.sub.c (100.4 mm) of the C-cassette 1 is the length of the cassette main body and does not include the side projections 1j. Therefore the overall length of the C-cassette 1 is slightly greater than 100.4 mm.
According to the specification of the D-cassette 2, the length and the width of the D-cassette 2 are the same as the C-cassette 1, namely it has a length L.sub.D of 100.4 mm and a width M.sub.D of 63.8 mm. The D-cassette 2 has a thickness N.sub.D of 9.6 mm which is thicker than the thickness N.sub.C.spsb.1 and thinner than the thickness N.sub.C.spsb.2 of the C-cassette 1. The depth n of the guide recession 2k of the D-cassette 2 is 2.5 mm.
Next, a cassette tape recorder which records and reproduces information on/from either the C-cassette 1 or D-cassette 2 is described below. Such a cassette tape recorder compatible with the C-cassette 1 and the D-cassette 2 performs both recording and reproduction in an automatic reverse mode with respect to the D-cassette 2 and at least plays the C-cassette 1 in the automatic reverse mode.
This cassette tape recorder has a cassette holder including just one cassette storage section capable of storing either the C-cassette 1 or the D-cassette 2. The cassette holder has a slider moving mechanism for opening and closing the slider 3 of the D-cassette 2. The cassette tape recorder has detecting means for detecting the type of a cassette stored in the cassette storage section. The detecting means enables the cassette storage section to store cassettes of different formats.
The cassette tape recorder has a rotary head mechanism 50 as shown in FIG. 14. As illustrated in FIG. 15, the rotary head mechanism 150 has a magnetic head 153 and head moving means 154 for moving the magnetic head 153. The magnetic head 153 is constituted by a digital head 151 (DH1 to DH9) and an analog head 152 (AH1 and AH2) aligned in a vertical direction on the same plane. The rotary head mechanism 150 rotates the magnetic head 153 by 180 degrees with the head moving means 154 to bring the respective heads 151 and 152 into the reversed state as shown in FIG. 16 so as to record or reproduce analog signals or digital signals in a suitable manner on/from a selected cassette (C-cassette or D-cassette).
The digital head 151 includes reproduction-use MR (magnetic resistance) heads and recording-use IH (inductive) head, while the analog head 152 includes only reproduction-use MR heads. Accordingly, the magnetic head 153 is capable of recording and reproducing information on/from the D-cassette 2 but incapable of recording information on the analog C-cassette 1. This is because overwriting is possible with respect to the D-cassette 2 but is not feasible with respect to the analog C-cassette 1. Therefore, an erase head is required to record information on the C-cassette 1. In other words, in order to record analog signals, an IH head and an erase head need to be disposed symmetrically on both sides of the MR head. Thus, this arrangement is not suitable for mass production since it requires five heads in total.
In order to enable the storage section to store cassettes of different formats, the cassette tape recorder needs to have a special device, for example, cassette detecting means, and a slider moving mechanism of a highly complicated structure. Consequently, the assembling process becomes complicated and the manufacturing costs increase substantially. Moreover, in the rotary mechanism 150, since the magnetic tape 1b or 2b of the cassette 1 or 2 is needed to be fed slidingly in contact with the magnetic head 153, the following problem arises.
Namely, a gap portion in the digital head 151 is much smaller than that in the analog head 152. The specification does not so strictly restrict the material of the magnetic tape 1b of the C-cassette 1 as it does with respect to the magnetic tape 2b of the D-cassette 2. Thus, when the magnetic tape 1b is fed past the magnetic head 153 while being made contact therewith, the magnetic powder of the magnetic tape 1b of the C-cassette 1 penetrates into the gaps in the digital head 151, causing the gaps to get clogged. As a result, the cassette tape recorder shows deterioration in the quality of the recording and reproduction with respect to the D-cassette 2.
To pursue an improvement in cost, the life of the magnetic head, and quality of recording and reproduction, it is beneficial to provide separate analog and digital heads for the C-cassette 1 and the D-cassette 2, respectively. In such a situation, the present applicant incorporated a cassette holder with two cassette storage sections, capable of storing two cassettes in a state where they are placed one upon another, into a cassette tape recorder compatible with C-cassette and D-cassette as disclosed in the Japanese Publication for Unexamined Utility Model Applications No. 178537/1986, No. 48039/1987, and No. 79855/1986.
Each of the cassette holders described in these publications stores two C-cassettes 1 placed one upon another. These cassette holders do not have a slider moving mechanism for opening and closing the slider 3 of the D-cassette 2 and therefore they are incompatible with the D-cassette 2. Moreover, it is difficult to incorporate a slider moving mechanism into these cassette holders due to the following reasons.
A cassette holder which has the slider moving mechanism and is capable of storing the C-cassette 1 and the D-cassette 2 one upon another needs to be movable between the load/unload position and the record/reproduction position. Recording and reproduction of information on the C-cassette 1 and the D-cassette 2 is available at the record/reproduction position. When the cassette holder is moved to the record/reproduction position, the C-cassette 1 and the D-cassette 2 are fixed in predetermined positions.
To hold the cassette 1 in a stationary state, the cassette holder disclosed in each of the above-mentioned publications has restricting means which restricts the level, i.e., the distance from the bottom of the holder storage section to the cassette 1 by supporting the back side of the cassettes 1 when the cassette holder comes into contact with the bottom of the holder storage section. Therefore, when the cassette holder is moved to the record/reproduction position, the location of the cassette 1 in the cassette storage section shifts in a direction opposite to the direction in which the cassette holder is moved because the restricting means support the cassette 1. Namely, the location of the cassette 1 relative to the cassette holder varies when the cassette holder is in the load/unload position and when it is in the record/reproduction position.
As for the D-cassette 2, since only the back side has the hollow sections 2e, it is stored in one cassette storage section more distant from the bottom of the holder storage section. Therefore, the slider moving mechanism is mounted on the top plate (i.e., a member constituting the cassette storage section, located farthest away from the bottom of the holder storage section) of the cassette holder.
When the cassette holder is in the load/unload position and the D-cassette 2 is loaded into the holder storage section, the slider moving member of the slider moving mechanism is inserted into the guide recession 2k. The inserted slider moving member comes into contact with the slider 3 and moves the slider 3.
However, when the above-mentioned restricting means is used as it is, the following problems arise. Namely, when the cassette holder having the D-cassette 2 in the holder storage section is moved to the record/reproduction position, the D-cassette 2 shifts to a direction opposite the direction in which the cassette is moved because it is supported by the restricting member. In other words, the D-cassette 2 is moved toward the top plate of the cassette holder whereupon the slider moving mechanism is mounted. Consequently, the positional relation between the slider moving member and the guide recession 2k changes.
Therefore, the edge of the slider moving member may crash into the bottom of the guide recession 2k due to the effects of the depth n (2.5 mm) of the guide recession 2k of the D-cassette 2, the amount of movement of the D-cassette 2, preciseness in the dimensions of the slider moving member, and inaccuracy of assembling. In other words, unless the preciseness in the dimensions of the restricting member and of parts of the slider moving mechanism are controlled very strictly, it is almost impossible to prevent the edge of the slider moving member from crashing into the bottom of the guide recession 2k. In reality, it is impossible to incorporate into the cassette holders of the above-mentioned publications a slider moving mechanism which properly opens the slider 3.